It is known that grinding aids of various types may be used to improve the cutting efficiency of resin bonded abrasive grain in grinding wheels and coated abrasives. Various combinations of abrasive grain and active filler materials supported in a resin bond have been suggested for improving grinding action of abrasive products and certain combinations have been found to be especially useful for grinding and/or cutting ferrous materials. It is known that the grinding performance of resin bonded grinding wheels can be significantly improved when active fillers are employed. A good active filler can help remove metal more efficiently and reduce the amount of heat generated in the grinding process which results in a decrease in required grinding energy and an increase in grinding wheel life.
Resin bonded grinding wheels including combinations of alumina and other abrasive grains with finely divided fillers such as cryolite, pyrite or FeS.sub.2, KAlF.sub.4, K.sub.3 AlF.sub.6, K.sub.2 SO.sub.4,PbCl.sub.2, PbO, Sb.sub.2 S.sub.3 and mixtures of these materials are known and used commercially. It has been found that certain combinations of fillers provide superior grinding quality when used in mixtures. For example, a mixture of FeS.sub.2 and K.sub.2 SO.sub.4 produces a synergistic effect when used in a phenolic bonded cut-off wheel with an alumina abrasive. While grinding wheels containing a mixture of FeS.sub.2 and K.sub.2 SO.sub.4 generally perform better than other prior art grinding wheels for many applications, the FeS.sub.2 /K.sub.2 SO.sub.4 wheel is relatively hard acting and burns the workpiece severly at moderate to low cutting rates. A grinding wheel which overcomes these problems is thus needed.
U.S. Pat. No. 4,475,926 disclosures a resinoid bonded abrasive article in which the resinoid bond includes 5-80% by volume of an improved active filler. The active filler is a mixture of iron pyrites, potassium sulfate, and an alkali haloferrate. In column 1, the patent discloses examples of various known fillers used in grinding wheel formations.
U.S. Pat. No. 2,258,774 discloses an organic bonded abrasive material containing certain low melting point metals such as lead, tin, bismuth, antimony, cadmium or alloys thereof. The metals are taught as being lubricants for the abrasive material.